I got my first red dot in 1985, I think. Perhaps earlier. I put an Aimpoint MkIII on the carry handle of an AR-15 now known as the SP1 version.
I've since had several. A couple of USPSA pistols with Tasco and C-Mores, ARs with Aimpoint Comps, a Vortex Sparc that has been on several rifles and is now on a Ruger MK III pistol.
My carry pistol is a Sig P320 with a Sig red dot (that I'm not entirely happy with). That gun will probably get a Trijicon RMR soon, and the Sig dot will go to a Sig P322...which I don't have yet.
Almost forgot:
My Ruger PC9 carbine has a Holosun green dot.
I prefer green and will get that whenever available. I first tried green in a Trijicon scope, loved it, and got another.
I have astigmatisms and some dots don't work well for me anymore. Some look like a comma, which is workable, but some are like looking at a stoplight through a rain-splattered windshield. I have heard EoTechs are best with astigmatism, but they are the worse for me. The green Holosun works the best for me.